Self propelled sawing machines with circular blades are used in the construction industry to make cuts in paving or floor materials such as concrete, masonry, etc. Current machines generally incorporate infinitely variable hydrostatic or mechanical transmissions in their drive trains to transmit power from the engine to the rear wheels for propulsion. The output speed and direction of rotation of the transmission is typically regulated or "shifted" by a remotely located manual control device connected by a linkage or cable to a control shaft on the transmission. The device, usually a lever and/or push-pull/vernier knob, is used by the operator as a coarse control to cause the machine to travel rapidly forward or in reverse for the purpose of maneuvering or positioning the machine for sawing. When operated as a fine control the device permits precise adjustment of forward speed, allowing the operator to set an optimum speed for the particular pavement material being sawn. "Optimum speed" in this case refers to the best overall propulsion speed for sawing when all the interacting variables such as aggregate hardness, machine power, blade design, operator skill, etc., are taken into account.
Optimum speed is determined empirically by the operator, who must subsequently move the control from the optimum setting each time it is necessary to maneuver the machine or if there is a need to make a temporary adjustment in travel speed when characteristics of the material being sawed change abruptly, e.g., steel reinforcing bar. The operator must then attempt to manually return the control to the previous optimum speed setting. However, this takes time in attempting to reach the same travel speed that has been made prior to the temporary adjustment or change of speed necessary to maneuver the machine. As a result, the efficiency of the sawing operation is reduced.
In order to improve the efficiency of a sawing operation as well as obtain other advantages, this invention has been made.